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Abstract:

The pouring nozzle comprises an elongated, tubular part (10), defining a
lower part of a pouring channel (12) with a central longitudinal axis L,
a plate-like part (14), provided with a flow-through opening (16) between
its surface (18) opposite the tubular part (10) and its section (20)
adjacent said tubular part (10). As may be seen from FIG. 2 the
flow-through opening (16) defines an upper part (12o) of the pouring
channel (12). The peripheral area (22) between said surface (18) and said
section (20) comprises four segments, namely two inclined bearing
surfaces (24), opposite to each other, and two planar surface sections
(26), arranged opposite and parallel to each other between said two
distinct bearing surfaces (24). Each bearing surface (24) is curved with
respect to the central longitudinal axis L of the pouring channel (12),
as may be best seen from FIG. 3. The curvature is therefore concave with
respect to the central longitudinal axis L and in view of the opposite
arrangement of the bearing surfaces (24) the said bearing surfaces are
arranged inversely to each other.

Claims:

1. Pouring nozzle comprising the following features: a) an elongated,
tubular part (10), defining a first part (12u) of a pouring channel (12)
with a central longitudinal axis (L), b) a plate like part (14), provided
with a flow-through opening (16) between its surface (18) opposite the
tubular part (10) and its section (20) adjacent said tubular part (10),
c) the flow-through opening (16) defining a second part (12o) of the
pouring channel (12), d) a peripheral area (22) between said surface (18)
and said section (20) comprising two bearing surfaces (24), e) each
bearing surface (24) provides at least one curvature, extending along an
imaginary plane perpendicular to the direction of the central
longitudinal axis (L), f) said bearing surfaces (24) are arranged
inversely.

3. Pouring nozzle according to claim 1, including a peripheral area (22)
comprising a) two distinct bearing surfaces (24) and b) two planar
surface sections (26) arranged parallel to each other and between said
two distinct bearing surfaces (24).

4. Pouring nozzle according to claim 1, wherein each of said two bearing
surfaces (24) provides a curvature of constant radius.

5. Pouring nozzle according to claim 1, wherein each of said two bearing
surfaces (24) provides a curvature, corresponding to a parabola in a
cross section perpendicular to the direction of the central longitudinal
axis (L) of said pouring channel (12).

6. Pouring nozzle according to claim 1, wherein each of said two bearing
surfaces (24) provides a curvature along an imaginary plane perpendicular
to the direction of the central longitudinal axis (L) of the pouring
channel (12) with a radius R2 being at least 2 times larger than the
diameter D of the flow through opening (16).

7. Pouring nozzle according to claim 1, wherein each of said two bearing
surfaces (24) provides said curvature, extending along an imaginary plane
comprising the central longitudinal axis (L) of the pouring channel (12)
which curvature extends in a direction from said surface (18) opposite to
the tubular part (10) to said section (20) adjacent said tubular part
(10) such that the bearing surfaces are part of a funnel shape.

8. Pouring nozzle according to claim 7, wherein said curvature is of
constant radius between its end opposite the tubular part (10) and said
section (20) adjacent said tubular part (10).

9. Pouring nozzle according to claim 7, wherein said curvature extends
partially between its end opposite the tubular part (10) and said section
(20) adjacent said tubular part (10).

10. Pouring nozzle according to claim 1 or 2, wherein each of said
bearing surfaces (24) provides a shape which corresponds to a partial
surface of one of the following geometrical shapes: paraboloid, cone,
dome, cylinder, torus.

11. Pouring nozzle according to claim 2, wherein each of said bearing
surfaces (24) provides a shape, which corresponds, in a longitudinal
section of the pouring nozzle, to at least one of the following
geometrical shapes: parabola, involute.

12. Pouring nozzle according to claim 1, wherein the said plate like part
(14) has a smaller cross sectional area at said section (20) adjacent
said tubular part (10) than at its end opposite the tubular part (10).

13. Pouring nozzle according to claim 1 made of ceramic refractory
material and designed as a one piece monolithic.

14. Pouring nozzle according to claim 1, wherein the said plate-like part
(14) and the said tubular part (10) are isostatically pressed parts.

15. Pouring nozzle according to claim 1, surrounded at least partially,
by a metallic envelope (28).

Description:

[0001] This invention relates to a pouring nozzle which nozzle serves for
the transfer of a metal melt from one (upper) metallurgical vessel like a
ladle to another (lower) metallurgical vessel such as a tundish.

[0002] In view of the harsh conditions during metal casting (temperatures
up to 1.700° C., chemical and metallurgical attack) such pouring
nozzle is usually made of a high temperature resistance ceramic
refractory material.

[0003] The pouring nozzle typically comprises an elongated, tubular part,
defining one part of a pouring channel with a central longitudinal axis
and a plate-like part, provided with a flow-through opening between its
surface opposite the tubular part and its section adjacent said tubular
part, wherein the flow-through opening defines a second part of said
pouring channel.

[0004] Insofar the general design of a pouring nozzle is more or less
identical, independently of whether it is used as a so called "inner
pouring nozzle", installed in the said upper metallurgical vessel (e.g. a
ladle) or used as an "outer pouring nozzle" following the said inner
pouring nozzle in the flow direction of the metallurgical melt. This
"outer pouring nozzle" may be designed as a "submerged entry nozzle".
Frequently it is designed as a "pouring nozzle for a nozzle insertion
and/or removal device", especially for a quick change during casting.

[0005] When used as an "inner pouring nozzle" the said plate-like part is
usually arranged at the lower end (in the flow direction of the melt)
while the outer pouring nozzle is arranged vice versa when used in a tube
changer.

[0006] In both cases means are provided for holding the nozzle precisely
in the desired position. Insofar known nozzles are provided with bearing
surfaces along the peripheral area of said plate-like part.

[0007] According to EP 1 289 696 B1 and EP 1 590 114 B1 the said
plate-like part comprises, on opposite sides, two planar bearing surfaces
forming an angle of 20° to 80° with the central
longitudinal axis of the pouring channel.

[0008] In use, the plate-like part of such pouring nozzles is held in
place against a corresponding plate-like part of another refractory
component. This other refractory component may, for example, be a
refractory plate component of a slide gate system, or may be the
plate-like part of a corresponding pouring nozzle. The plate-like parts
are subjected to different levels of thermal expansion in the region
adjacent to the pouring channel and the region most distant from the
pouring channel. This can cause the otherwise flat plate-like part to be
caused to bend to accommodate the higher level of expansion in the region
of the pouring channel. The effect of this is that the area of contact
between the plate-like parts of the pouring nozzles and their
corresponding other refractory component is decreased, and becomes
limited to a relatively small annular section circumscribing the pouring
channel. This creates a number of risks. Firstly, the thermo-mechanical
stresses induced by the differential expansion across the plate-like
region can give rise to the propagation of micro-cracks or cracks within
said plate-like part and/or in the region between said plate-like part
and the adjacent tubular-like part. Secondly, the reduced area of contact
leads to a diminished sealing between the refractory components which can
allow air ingress to the molten metal stream (leading to oxidation and
deterioration in the quality of the cast steel) or, conversely, leakage
of molten steel.

[0009] In this respect there is a permanent demand to increase and
optimize the design, the safety and/or the use of said type of nozzles.

[0010] Typically a number of pushing devices (pushing cylinders) are
acting on each bearing surface. These pushing devices are arranged side
by side (in parallel) in a way that their respective forces of pressure
are more or less parallel to each other. Each of them exercises a more or
less identical force onto the corresponding part of the bearing surface.
However, these forces are not necessarily directed to the region of the
plate-like part around the pouring channel to which the contact area is
restricted and where the thermo-mechanically stresses are greatest. This
limitation is overcome by the design of pouring nozzles of the present
invention wherein the respective bearing surfaces are curved instead of
planar.

[0011] Applicant's invention provides a pouring nozzle of the type
mentioned with improved stress distribution in the plate and focussing
the pushing forces towards the area around the pouring channel.

[0012] The invention replaces the planar bearing surface according to
prior art by a curved bearing surface, including a bearing surface being
curved with respect to the central longitudinal axis of the pouring
channel. This makes it possible to exert pressure forces in a more
concentric manner (with respect to the central longitudinal axis of the
pouring channel) into the refractory material.

[0013] In its most general embodiment the invention relates to a pouring
nozzle comprising the following features: [0014] an elongated, tubular
part, defining a first part of a pouring channel with a central
longitudinal axis, [0015] a plate-like part provided with a flow-through
opening between its surface opposite the tubular part and its section
adjacent said tubular part, [0016] the flow-through opening defining a
second part of the pouring channel, [0017] a peripheral area between said
surface and said section comprising two bearing surfaces, [0018] each
bearing surface provides at least one curvature, extending along an
imaginary plane perpendicular to the direction of the central
longitudinal axis (L), [0019] said bearing surfaces are arranged
inversely.

[0020] The inverse arrangement of the bearing surfaces leads to a design
of the plate-like part of the pouring nozzle which may be mirror-inverted
with respect to an imaginary longitudinal plane including the central
longitudinal axis of the pouring channel.

[0021] In a preferred embodiment the peripheral area comprises two
distinct bearing surfaces and two planar surface sections arranged
parallel to each other and between said two distinct bearing surfaces. In
other words: The peripheral area of the plate-like part is as follows:
One curved bearing surface is followed by a planar surface section, which
then is followed by the second curved bearing surface and the latter then
again followed by a planar surface section. The plate like part typically
is of rectangular/square shape (seen from above). A corresponding design
is shown in the attached drawings.

[0022] The said curvature of the bearing surfaces may be of a constant
radius or can vary along the bearing surface. This enables to provide
radial forces from the pushing devices into the plate like section of the
nozzle. Depending on the curvature the pressure forces do not extend any
more parallel to each other but in a converging manner.

[0023] According to another embodiment the said two bearing surfaces each
provide a curvature corresponding to a parabola in a cross section
perpendicular to the central longitudinal axis of said pouring channel.

[0024] The design described above presents a nozzle with two bearing
surfaces each of which being characterized by a curvature along an
imaginary plane, which imaginary plane is perpendicular or inclined
respectively to the direction of the central longitudinal axis of the
pouring channel. This design includes embodiments wherein a radius
R2 or R3 of said curvature is larger than the diameter D of the
flow through opening (bore), e.g. more than 2 times larger or more than 3
times larger, more than 5 times larger or more than 10 times larger.

[0025] According to another embodiment each of said two bearing surfaces
may in addition provide a curvature, extending along an imaginary plane
comprising the longitudinal axis of the pouring channel, which curvature
extends in a direction from said surface opposite the tubular part to
said section adjacent said tubular part.

[0026] Said second type of curvature may be of constant radius between its
end opposite the tubular part and said section adjacent said tubular part
but typically it will have different radiuses along its extension.

[0027] This includes an embodiment wherein said second curvature extends
only partially between one end of the plate-like part opposite the
tubular part and its second end adjacent said tubular part.

[0028] The said bearing surfaces, curved all over its area and/or along a
part of it may provide a shape which corresponds at least partially to a
partial surface (segment) of one of the following geometrical shapes:
cylinder, paraboloid, cone, dome, toroid.

[0029] In a longitudinal section the shape of said bearing surfaces may
correspond at least partially to at least one of the following
geometrical shapes: Parabola, involute, ellipse. Alternatively the
bearing surface in the longitudinal section may be linear.

[0030] Typically the said plate-like part has a smaller cross sectional
area at its section adjacent said tubular part than at its end opposite
said tubular part. This leads to an arrangement whereby the pushing
forces applied to the bearing surfaces are directed in part upwardly (for
the outer pouring nozzle) or downwardly (for the inner pouring nozzle),
respectively. In other words: The pushing forces have a vector component
in the direction of the corresponding surface of the respective plate
like part in order to improve the tightness of said surface to the
adjacent component of the system, e.g. a sliding plate of a slide gate
valve or the surface of a second nozzle.

[0031] In addition the curvature of the bearing surfaces will for all
pushing devices concentrate a part of said vector component in the
direction of the pouring channel and thereby minimizing the risks arisen
from the reduced area of contact created by the differential thermal
expansion of the plate like part in use.

[0032] The said pouring nozzle may be made of a ceramic refractory
material and designed as one piece (so called monotube). It may also be
made of separate parts, for example the tubular part and the plate-like
part which are then fixed to each other by a common outer metallic
envelope and/or a bonding agent (an adhesive).

[0033] The nozzle and/or its parts may be pressed isostatically.

[0034] Further features of the invention may be derived from the other
application documents and/or the sub claims.

[0035] The invention will be described in more detail in accordance with
the attached drawings. These drawings schematically show the following:

[0036] FIG. 1: a 3-dimensional view of a pouring nozzle,

[0037] FIG. 2: a longitudinal sectional view of the nozzle in accordance
with FIG. 1.

[0038] FIG. 3: a cross-sectional view of the nozzle in accordance with
FIGS. 1, 2 in the area of pushing devices (C-C of FIG. 2),

[0039] FIG. 4: a 3-dimensional view of a second embodiment,

[0040] FIG. 5: a longitudinal sectional view of the nozzle in accordance
with FIG. 4,

[0041] FIG. 6: a longitudinal sectional view of a third embodiment.

[0042] Identical parts or parts providing the same function are designated
by same numerals.

[0043] According to FIG. 1 the pouring nozzle comprises an elongated,
tubular part 10, defining a lower part of a pouring channel 12 with a
central longitudinal axis L, a plate-like part 14, provided with a
flow-through opening 16 between its surface 18 opposite the tubular part
10 and its section 20 adjacent said tubular part 10. As may be seen from
FIG. 2 the flow-through opening 16 defines an upper part 12o of the
pouring channel 12.

[0044] The peripheral area 22 between said surface 18 and said section 20
comprises four segments, namely two inclined bearing surfaces 24,
opposite to each other, and two planar surface sections 26, arranged
opposite and parallel to each other between said two distinct bearing
surfaces 24.

[0045] Each bearing surface 24 is curved with respect to the central
longitudinal axis L of the pouring channel 12, as may be best seen from
FIG. 3. The curvature is therefore concave with respect to the central
longitudinal axis L and in view of the opposite arrangement of the
bearing surfaces 24 the said bearing surfaces are arranged inversely to
each other.

[0046] In FIG. 2 the diameter of the flow-through opening 16 is marked as
D while the radius of the corresponding curved bearing surface 24 is
marked as R3 with R3>D. Radius R3 lies in a plane
inclined to the longitudinal axis L of pouring channel 12. Radius R4
of curved bearing surface describes the design along the longitudinal
sectional view of this figure.

[0047] Each bearing surface 24 provides an additional curvature extending
in a direction from said surface 18 to said section 20 as may be seen
best from FIG. 2. Said additional curvature has the shape of a quadrant
and is arranged at a distance from said surface 18, as may been seen from
FIG. 2.

[0048] The peripheral area 22 of plate-like part 14 and the adjacent upper
section of tubular part 10 are enclosed by a metallic envelope 28, which
is shrunk or cemented onto the corresponding surface sections.

[0049] The shown nozzle with tubular part 10 and plate-like part 14 was
pressed isostatically to provide a monolithic ceramic refractory body
(monotube design) before the metallic envelope 28 was fitted as
described.

[0050] It may be used as an outer nozzle (in the orientation according to
FIG. 1, 2) or as an inner nozzle by inverting through 180° or
upside down.

[0051] As may be seen from FIGS. 1 and 3 three pushing devices 301, 30m
and 30r are arranged along each of said bearing surfaces 24 in a row.

[0052] Pushing device 30m is arranged in such a way so that its pushing
force, characterized by arrow Pm is exactly directed towards the
central longitudinal axis L of the pouring channel 12.

[0053] Pushing devices 301 and 30r on opposite sides with respect to
pushing device 30m are arranged such that their corresponding pushing
forces P1, Pr as transmitted by the bearing surfaces 24 through
the plate-like part 14 do not run parallel to pushing force Pm but
slightly inclined towards the central longitudinal axis L without running
through it.

[0054] This arrangement secures an increased and optimized fixation as
well as optimized centering of the nozzle within a corresponding (not
shown) clamping device while at the same time decreasing the risk of
crack formation within the ceramic refractory material of plate-like part
14.

[0055] As may be seen from FIGS. 1 and 2 the said pushing devices 301, 30m
and 30r are further arranged in such a way that the resulting thrust
forces are applied with a vertical component in the direction of surface
18.

[0056] In FIGS. 4 and 6 two alternative embodiments are shown.

[0057] In FIG. 4 the bearing surfaces 24 of the nozzle are part of a
frustocone. The longitudinal cross section of the nozzle is shown in FIG.
5. The mean radius of this frustocone is R2. The longitudinal cross
section according to FIG. 6 shows a similar curvature of the bearing
surfaces 24 of the embodiment in FIG. 2 but the radius R2 is in an
imaginary plane perpendicular to the longitudinal axis L of pouring
channel 12.